Normally, searching of viewing field in charged particle beam apparatus including an imaging device is performed by acquiring a captured image of a sample placed on an sample table by an imaging device and selecting a position or a range on the sample to be observed by being irradiated with an electron beam by the charged particle beam apparatus as a viewing field range within an acquired captured image of the sample table and the sample. In the charged particle beam apparatus, an observation range on the sample irradiated with a charged particle beam is set from data of the captured image relating to the selected viewing field range, and an observation image relating to the viewing field range of the sample is obtained by irradiating the observation range with the charged particle beam.
In the searching of viewing field, the acquisition of the captured image of the sample table and the sample by the imaging device is performed by appropriately enlarging/reducing the sample table on which the sample is placed to image the sample table. The selection of the viewing field range is performed by specifying a desired position and range on the captured image displayed by a display device. Therefore, in a case where the imaging device or the captured image of which an enlargement magnification is unknown is used for selection of the viewing field range, in order to acquire the observation range on the sample irradiated with the charged particle beam from the selected viewing field range, it is necessary to specify an imaging magnification of the captured image acquired by being appropriately enlarged/reduced.
Therefore, in order to specify the imaging magnification of the captured image of the sample table and the sample acquired by the imaging device, in a scanning electron microscope disclosed in Patent PTL 1, an adjustment guide for sample table recognition having the same shape as that of the sample table in an optical image, is displayed on a display screen on which an optical image of the sample table and the sample of the display device imaged by an optical imaging device is displayed to identify a size of the sample table in the optical image, and the adjustment guide is enlarged reduced/moved on the display screen to make it coincide with the optical image of the sample table on the display screen, thereby recognizing the size and a center position of the sample table on the optical image. The enlargement magnification of the optical image acquired by the optical imaging device and the center position of the sample table on the optical image are calculated based on a correspondence between the size of the recognized optical image of the sample table on the display screen and an actual size of the sample table stored in advance, and are used in alignment when being observed by the charged particle beam apparatus.